1. Field of the Invention
The present invention relates to a printing device for printing images by ejecting a plurality of inks onto printing media.
2. Description of the Related Art
In recent years, ink jet printers have come to enjoy widespread use as image printing devices. Users may select desired print media from among a variety of available types for use in ink jet printers. Such print media include, for example, “glossy” paper having relatively high gloss, “plain” paper having relatively low gloss, matte paper, and so on.
The amount of ink that is ejected onto printing media is determined by the image data that is to be printed. Greater amounts of ink are ejected in areas of low brightness, and lower amounts of ink are ejected in areas of higher brightness.
When an image is printed on a printing medium of relatively high gloss, the gloss tends to be more intense in areas where more ink has been ejected. For example, when images of human figures are printed against a white background, the gloss is higher in areas with human figures, which is where greater amounts of ink are ejected, and the gloss is lower in the background area, where less ink is ejected. A resulting problem is that a person viewing the image experiences unpleasant impression of different levels of gloss in different areas of the same image.
When the image is printed on a printing medium of relatively low gloss, on the other hand, the ink tends to be absorbed by the printing medium. As a result, less ink colorant remains on the surface of the printing medium, and areas which are supposed to be covered by the ink on the printing medium do not develop on the surface, making it difficult to attain the desired coloring. The unevenness of coloring is especially noticeable in areas where large amounts of ink have been ejected, such as areas in which ink has been ejected on virtually all of the pixels. When images of human figures are printed against a white background, for example, the unevenness of coloring will occur in the area of the human figures containing a greater amount of ink, causing graininess in the image.
In short, conventional printing with ordinary inks sometimes cannot attain satisfactory image quality.